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1.
Sci Rep ; 12(1): 19178, 2022 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-36357418

RESUMO

A large set of nucleobases and amino acids is found in meteorites, implying that several chemical reservoirs are present in the solar system. The "geochemical continuity" hypothesis explores how protometabolic paths developed from so-called "bricks" in an enzyme-free prebiotic world and how they affected the origins of life. In the living cell, the second step of synthesizing uridine and cytidine RNA monomers is a carbamoyl transfer from a carbamoyl donor to aspartic acid. Here we compare two enzyme-free scenarios: aqueous and mineral surface scenarios in a thermal range up to 250 °C. Both processes could have happened in ponds under open atmosphere on the primeval Earth. Carbamoylation of aspartic acid with cyanate in aqueous solutions at 25 °C gives high N-carbamoyl aspartic acid yields within 16 h. It is important to stress that, while various molecules could be efficient carbamoylating agents according to thermodynamics, kinetics plays a determining role in selecting prebiotically possible pathways.


Assuntos
Ácido Aspártico , Uracila , Uracila/química , Carbamilação de Proteínas , Lagoas , Esqueleto , Origem da Vida
2.
Life (Basel) ; 12(11)2022 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-36362844

RESUMO

The role of minerals in the chemical evolution of RNA molecules is an important issue when considering the early stage of the Hadean Earth. In particular, the interaction between functional ribozymes and ancient minerals under simulated primitive conditions is a recent research focus. We are currently attempting to design a primitive RNA metabolic network which would function with minerals, and believe that the simulated chemical network of RNA molecules would be useful for evaluation of the chemical evolution from a simple RNA mixture to an RNA-based life-like system. First, we measured the binding interactions of oligonucleotides with four types of minerals; Aerosil silica, zirconium silicate, sepiolite, and montmorillonite. Oligonucleotides bound zirconium silicate and montmorillonite in the presence of MgCl2, and bound sepiolite both in the presence and absence of MgCl2, but they did not bind Aerosil. Based on the binding behavior, we attempted the self-cleavage reaction of the hammerhead ribozyme from an avocado viroid. This reaction was strongly inhibited by zirconium silicate, a compound regarded as mineral evidence for the existence of water. The present study suggests that the chemical evolution of functional RNA molecules requires specific conformational binding, resulting in efficient ribozyme function as well as zirconium silicate for the chemical evolution of biomolecules.

3.
Life (Basel) ; 12(8)2022 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-36013404

RESUMO

The RNA world hypothesis suggests that chemical networks consisting of functional RNA molecules could have constructed a primitive life-like system leading a first living system. The chemical evolution scenario of RNA molecules should be consistent with the Hadean Earth environment. We have demonstrated the importance of the environment at both high temperature and high pressure, using different types of hydrothermal flow reactor systems and high-pressure equipment. In the present study, we have attempted to develop an alternative easy-to-implement method for high-pressure measurements and demonstrate that the system is applicable as an efficient research tool for high-pressure experiments at pressures up to 30 MPa. We demonstrate the usefulness of the system by detecting the high-pressure influence for the self-cleavage of avocado hammerhead ribozyme (ASBVd(-):HHR) at 45-65 °C. A kinetic analysis of the high-pressure behavior of ASBVd(-):HHR shows that the ribozyme is active at 30 MPa and its activity is sensitive to pressures between 0.1-30 MPa. The surprising finding that such a short ribozyme is effective for self-cleavage at a high pressure suggests the importance of pressure as a factor for selection of adaptable RNA molecules towards an RNA-based life-like system in the Hadean Earth environment deep in the ocean.

4.
Biology (Basel) ; 10(8)2021 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-34439952

RESUMO

A high pressure apparatus allowing one to study enzyme kinetics under pressure was used to study the self-cleavage activity of the avocado sunblotch viroid. The kinetics of this reaction were determined under pressure over a range up to 300 MPa (1-3000 bar). It appears that the initial rate of this reaction decreases when pressure increases, revealing a positive ΔV≠ of activation, which correlates with the domain closure accompanying the reaction and the decrease of the surface of the viroid exposed to the solvent. Although, as expected, temperature increases the rate of the reaction whose energy of activation was determined, it appeared that it does not significantly influence the ΔV≠ of activation and that pressure does not influence the energy of activation. These results provide information about the structural aspects or this self-cleavage reaction, which is involved in the process of maturation of this viroid. The behavior of ASBVd results from the involvement of the hammerhead ribozyme present at its catalytic domain, indeed a structural motif is very widespread in the ancient and current RNA world.

5.
Sci Rep ; 11(1): 19356, 2021 09 29.
Artigo em Inglês | MEDLINE | ID: mdl-34588537

RESUMO

The first step of pyrimidine synthesis along the orotate pathway is studied to test the hypothesis of geochemical continuity of protometabolic pathways at the origins of life. Carbamoyl phosphate (CP) is the first high-energy building block that intervenes in the in vivo synthesis of the uracil ring of UMP. Thus, the likelihood of its occurrence in prebiotic conditions is investigated herein. The evolution of carbamoyl phosphate in water and in ammonia aqueous solutions without enzymes was characterised using ATR-IR, 31P and 13C spectroscopies. Carbamoyl phosphate initially appears stable in water at ambient conditions before transforming to cyanate and carbamate/hydrogenocarbonate species within a matter of hours. Cyanate, less labile than CP, remains a potential carbamoylating agent. In the presence of ammonia, CP decomposition occurs more rapidly and generates urea. We conclude that CP is not a likely prebiotic reagent by itself. Alternatively, cyanate and urea may be more promising substitutes for CP, because they are both "energy-rich" (high free enthalpy molecules in aqueous solutions) and kinetically inert regarding hydrolysis. Energy-rich inorganic molecules such as trimetaphosphate or phosphoramidates were also explored for their suitability as sources of carbamoyl phosphate. Although these species did not generate CP or other carbamoylating agents, they exhibited energy transduction, specifically the formation of high-energy P-N bonds. Future efforts should aim to evaluate the role of carbamoylating agents in aspartate carbamoylation, which is the following reaction in the orotate pathway.

6.
Chem Rev ; 120(11): 4898-4918, 2020 06 10.
Artigo em Inglês | MEDLINE | ID: mdl-31804075

RESUMO

The use of high hydrostatic pressure to investigate structure-function relationships in biomacromolecules in solution provides precise information about conformational changes and variations of the interactions between these macromolecules and the solvent, as well as the volume changes associated with their activity. The complementary use of osmotic pressure reveals quantitatively the extent and direction of the water exchanges between the macromolecules and the solvent and the number of water molecules involved in these exchanges. In this review, the chemistry of ribozymes and the influence of pressure is described. In the case of the hairpin ribozyme, pressure slowed down the self-cleavage reaction on the basis that the formation of the transition state involves a positive ΔV⧧ of activation and the release of 78 ± 4 water molecules. The self-cleaving activity of the hammerhead ribozyme is also slowed down by pressure on the basis of kinetic parameters and ΔVs comparable to those of the hairpin ribozymes. However, it appears that the solution of the hammerhead ribozyme used in this study contains two populations of molecules which differ by the values of these parameters. The results obtained in the case of small self-cleaving ribozymes containing adenine bulges are consistent with the hypothesis that these small RNAs that bind amino acids or peptides could have appeared in prebiotic chemistry under extreme conditions in deep-sea vents or hydrothermal surface sites.


Assuntos
Pressão Hidrostática , Pressão Osmótica , RNA Catalítico/química , Aminoácidos/química , Aminoácidos/metabolismo , Evolução Química , Cinética , Concentração Osmolar , Peptídeos/química , Peptídeos/metabolismo , Conformação Proteica , RNA Catalítico/metabolismo
7.
Cell Tissue Res ; 379(3): 635-645, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31788759

RESUMO

In human, the use of freshly recovered granulosa cells for experiments remains difficult. Because of the single use of human cells, the experiments cannot be repeated, and no additional conditions can be tested afterwards with the cells of the same patient. Therefore, granulosa cell cryopreservation could be a good alternative to keep part of these cells for later controls or experiments. The aim of this study is to compare the responsiveness to FSH of fresh and frozen-thawed human primary granulosa-lutein cells (hGLC) and determine if cryopreserved granulosa cells can be used in place of fresh cells. Two cryopreservation methods were also compared: a conventional versus a simplified freezing method. This experimental study was undertaken at Igyxos S.A., Nouzilly, France. Seventy women undergoing oocyte retrieval at the IVF Unit from Bretonneau University Hospital (Tours, France) were recruited in 2016. Fresh and frozen-thawed hGLC were cultured for 7 days and then stimulated by r-FSH for 48 h. To assess r-FSH efficacy and potency, extracellular cAMP accumulated in the supernatant for each stimulation point was measured. We demonstrated that hGLC remain responsive to FSH stimulation after freezing-thawing and 7 days of pre-culture. They are able to secrete cAMP with a similar EC50 value as fresh hGLC, but FSH efficacy is lowered. As our study did not show any significant difference between the two freezing methods concerning the sensitivity of hGLC to FSH, hGLC could be cryopreserved with the simplified freezing method without taking up too much time for IVF laboratories.


Assuntos
Criopreservação/métodos , Gonadotropinas/farmacologia , Células da Granulosa/citologia , Células da Granulosa/efeitos dos fármacos , Células Cultivadas , Feminino , Humanos
8.
Life (Basel) ; 9(4)2019 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-31717814

RESUMO

Space missions using probes to return dust samples are becoming more frequent. Dust collectors made of silica aerogel blocks are used to trap and bring back extraterrestrial particles for analysis. In this work, we show that it is possible to detect traces of adenine using surface-enhanced Raman spectroscopy (SERS). The method was first optimized using adenine deposition on glass slides and in glass wells. After this preliminary step, adenine solution was injected into the silica aerogel. Finally, gaseous adenine was successfully trapped in the aerogel. The presence of traces of adenine was monitored by SERS through its characteristic bands at 732, 1323, and 1458 cm-1 after the addition of the silver Creighton colloid. Such a method can be extended in the frame of Tanpopo missions for studying the interplanetary transfer of prebiotic organic compounds of biological interest.

9.
Orig Life Evol Biosph ; 49(3): 111-145, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31399826

RESUMO

In this review, we describe some of the central philosophical issues facing origins-of-life research and provide a targeted history of the developments that have led to the multidisciplinary field of origins-of-life studies. We outline these issues and developments to guide researchers and students from all fields. With respect to philosophy, we provide brief summaries of debates with respect to (1) definitions (or theories) of life, what life is and how research should be conducted in the absence of an accepted theory of life, (2) the distinctions between synthetic, historical, and universal projects in origins-of-life studies, issues with strategies for inferring the origins of life, such as (3) the nature of the first living entities (the "bottom up" approach) and (4) how to infer the nature of the last universal common ancestor (the "top down" approach), and (5) the status of origins of life as a science. Each of these debates influences the others. Although there are clusters of researchers that agree on some answers to these issues, each of these debates is still open. With respect to history, we outline several independent paths that have led to some of the approaches now prevalent in origins-of-life studies. These include one path from early views of life through the scientific revolutions brought about by Linnaeus (von Linn.), Wöhler, Miller, and others. In this approach, new theories, tools, and evidence guide new thoughts about the nature of life and its origin. We also describe another family of paths motivated by a" circularity" approach to life, which is guided by such thinkers as Maturana & Varela, Gánti, Rosen, and others. These views echo ideas developed by Kant and Aristotle, though they do so using modern science in ways that produce exciting avenues of investigation. By exploring the history of these ideas, we can see how many of the issues that currently interest us have been guided by the contexts in which the ideas were developed. The disciplinary backgrounds of each of these scholars has influenced the questions they sought to answer, the experiments they envisioned, and the kinds of data they collected. We conclude by encouraging scientists and scholars in the humanities and social sciences to explore ways in which they can interact to provide a deeper understanding of the conceptual assumptions, structure, and history of origins-of-life research. This may be useful to help frame future research agendas and bring awareness to the multifaceted issues facing this challenging scientific question.


Assuntos
Biologia/história , Química/história , Historiografia , Informática/história , Origem da Vida , Paleontologia/história , Filosofia/história , História do Século XVI , História do Século XVII , História do Século XVIII , História do Século XIX , História do Século XX , História do Século XXI , Biologia Molecular/história
10.
Viruses ; 11(3)2019 03 21.
Artigo em Inglês | MEDLINE | ID: mdl-30901893

RESUMO

Current cellular facts allow us to follow the link from chemical to biochemical metabolites, from the ancient to the modern world. In this context, the "RNA world" hypothesis proposes that early in the evolution of life, the ribozyme was responsible for the storage and transfer of genetic information and for the catalysis of biochemical reactions. Accordingly, the hammerhead ribozyme (HHR) and the hairpin ribozyme belong to a family of endonucleolytic RNAs performing self-cleavage that might occur during replication. Furthermore, regarding the widespread occurrence of HHRs in several genomes of modern organisms (from mammals to small parasites and elsewhere), these small ribozymes have been regarded as living fossils of a primitive RNA world. They fold into 3D structures that generally require long-range intramolecular interactions to adopt the catalytically active conformation under specific physicochemical conditions. By studying viroids as plausible remains of ancient RNA, we recently demonstrated that they replicate in non-specific hosts, emphasizing their adaptability to different environments, which enhanced their survival probability over the ages. All these results exemplify ubiquitous features of life. Those are the structural and functional versatility of small RNAs, ribozymes, and viroids, as well as their diversity and adaptability to various extreme conditions. All these traits must have originated in early life to generate novel RNA populations.


Assuntos
RNA Catalítico/química , RNA Catalítico/genética , RNA Viral/genética , Viroides/genética , Conformação de Ácido Nucleico
11.
Artigo em Inglês | MEDLINE | ID: mdl-30833928

RESUMO

Gonadotropins are essential for reproduction control in humans as well as in animals. They are widely used all over the world for ovarian stimulation in women, spermatogenesis stimulation in men, and ovulation induction and superovulation in animals. Despite the availability of many different preparations, all are made of the native hormones. Having different ligands with a wide activity range for a given receptor helps better understand its molecular and cellular signaling mechanisms as well as its physiological functions, and thus helps the development of more specific and adapted medicines. One way to control the gonadotropins' activity could be the use of modulating antibodies. Antibodies are powerful tools that were largely used to decipher gonadotropins' actions and they have shown their utility as therapeutics in several other indications such as cancer. In this review, we summarize the inhibitory and potentiating antibodies to gonadotropins, and their potential therapeutic applications.

12.
J Phys Chem Lett ; 9(17): 4981-4987, 2018 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-30107125

RESUMO

Understanding the mechanism of spontaneous formation of ribonucleotides under realistic prebiotic conditions is a key open issue of origins-of-life research. In cells, de novo and salvage nucleotide enzymatic synthesis combines 5-phospho-α-d-ribose-1-diphosphate (α-PRPP) and nucleobases. Interestingly, these reactants are also known as prebiotically plausible compounds. Combining ab initio molecular dynamics simulations with recently developed reaction exploration and enhanced sampling methods, we show that nucleobases and α-PRPP should spontaneously combine, under mild hydrothermal conditions, with an exothermic reaction and a facile mechanism, forming both purine and pyrimidine ribonucleotides. Surprisingly, this mechanism is very similar to the biological one and yields ribonucleotides with the same anomeric carbon chirality as in biological systems. Mass spectrometry experiments performed on solutions of adenine and PRPP in similar conditions support the formation of AMP. These results suggest that natural selection might have optimized, through enzymes, a pre-existing ribonucleotide formation mechanism, carrying it forward to modern life forms.


Assuntos
Simulação de Dinâmica Molecular , Teoria Quântica , RNA/química , Ribonucleotídeos/síntese química , Conformação de Ácido Nucleico , Prebióticos , Ribonucleotídeos/química
13.
Angew Chem Int Ed Engl ; 56(27): 7920-7923, 2017 06 26.
Artigo em Inglês | MEDLINE | ID: mdl-28558156

RESUMO

In this contribution, we report the formation under prebiotic conditions of phosphoribosyl pyrophosphate (PRPP) as a molecular precursor in the one-pot synthesis of a canonical nucleotide, namely adenosine monophosphate (AMP) from its building blocks (KH2 PO4 or Pi , adenine, and d-ribose), on a fumed silica surface. The on-the-rocks approach has been successfully applied to the simultaneous phosphorylation and glycosylation of ribose. The one-pot formation mechanism of AMP involves a two-step pathway via an activated intermediate, namely PRPP, obtained by multiple ribose phosphorylations upon mild thermal activation.

14.
Orig Life Evol Biosph ; 47(3): 281-296, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28432500

RESUMO

Here we overview the chemical evolution of RNA molecules from inorganic material through mineral-mediated RNA formation compatible with the plausible early Earth environments. Pathways from the gas-phase reaction to the formation of nucleotides, activation and oligomerization of nucleotides, seem to be compatible with specific environments. However, how these steps interacted is not clear since the chemical conditions are frequently different and can be incompatible between them; thus the products would have migrated from one place to another, suitable for further chemical evolution. In this review, we summarize certain points to scrutinize the RNA World hypothesis.


Assuntos
Planeta Terra , Evolução Química , Origem da Vida , RNA/química , Minerais/química , Nucleotídeos/química , Fenômenos de Química Orgânica
15.
Life (Basel) ; 7(1)2017 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-28054992

RESUMO

An essential question in studies on the origins of life is how nucleic acids were first synthesized and then incorporated into compartments about 4 billion years ago. A recent discovery is that guided polymerization within organizing matrices could promote a non-enzymatic condensation reaction allowing the formation of RNA-like polymers, followed by encapsulation in lipid membranes. Here, we used neutron scattering and deuterium labelling to investigate 5'-adenosine monophosphate (AMP) molecules captured in a multilamellar phospholipid matrix. The aim of the research was to determine and compare how mononucleotides are captured and differently organized within matrices and multilamellar phospholipid structures and to explore the role of water in organizing the system to determine at which level the system becomes sufficiently anhydrous to lock the AMP molecules into an organized structure and initiate ester bond synthesis. Elastic incoherent neutron scattering experiments were thus employed to investigate the changes of the dynamic properties of AMP induced by embedding the molecules within the lipid matrix. The influence of AMP addition to the lipid membrane organization was determined through diffraction measurement, which also helped us to define the best working Q range for dynamical data analysis with respect to specific hydration. The use of different complementary instruments allowed coverage of a wide time-scale domain, from ns to ps, of atomic mean square fluctuations, providing evidence of a well-defined dependence of the AMP dynamics on the hydration level.

16.
Sci Rep ; 6: 37138, 2016 11 16.
Artigo em Inglês | MEDLINE | ID: mdl-27849042

RESUMO

Conformational changes associated with ribosome function have been identified by X-ray crystallography and cryo-electron microscopy. These methods, however, inform poorly on timescales. Neutron scattering is well adapted for direct measurements of thermal molecular dynamics, the 'lubricant' for the conformational fluctuations required for biological activity. The method was applied to compare water dynamics and conformational fluctuations in the 30 S and 50 S ribosomal subunits from Haloarcula marismortui, under high salt, stable conditions. Similar free and hydration water diffusion parameters are found for both subunits. With respect to the 50 S subunit, the 30 S is characterized by a softer force constant and larger mean square displacements (MSD), which would facilitate conformational adjustments required for messenger and transfer RNA binding. It has been shown previously that systems from mesophiles and extremophiles are adapted to have similar MSD under their respective physiological conditions. This suggests that the results presented are not specific to halophiles in high salt but a general property of ribosome dynamics under corresponding, active conditions. The current study opens new perspectives for neutron scattering characterization of component functional molecular dynamics within the ribosome.


Assuntos
Haloarcula marismortui/química , Simulação de Dinâmica Molecular , RNA Arqueal/química , RNA Mensageiro/química , Subunidades Ribossômicas Maiores de Arqueas/química , Subunidades Ribossômicas Menores de Arqueas/química , Difração de Nêutrons
17.
Chemistry ; 22(44): 15834-15846, 2016 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-27624284

RESUMO

Understanding ribose reactivity is a crucial step in the "RNA world" scenario because this molecule is a component of all extant nucleotides that make up RNA. In solution, ribose is unstable and susceptible to thermal destruction. We examined how ribose behaves upon thermal activation when adsorbed on silica, either alone or with the coadsorption of inorganic salts (MgCl2 , CaCl2 , SrCl2 , CuCl2 , FeCl2 , FeCl3 , ZnCl2 ). A combination of 13 C NMR, in situ IR, and TGA analyses revealed a variety of phenomena. When adsorbed alone, ribose remains stable up to 150 °C, at which point ring opening is observed, together with minor oxidation to a lactone. All the metal salts studied showed specific interactions with ribose after dehydration, resulting in the formation of polydentate metal ion complexes. Anomeric equilibria were affected, generally favoring ribofuranoses. Zn2+ stabilized ribose up to higher temperatures than bare silica (180 to 200 °C). Most other cations had an adverse effect on ribose stability, with ring opening already upon drying at 70 °C. In addition, alkaline earth cations catalyzed the dehydration of ribose to furfural and, to variable degrees, its further decarbonylation to furan. Transition-metal ions with open d-shells took part in redox reactions with ribose, either as reagents or as catalysts. These results allow the likelihood of prebiotic chemistry scenarios to be evaluated, and may also be of interest for the valorization of biomass-derived carbohydrates by heterogeneous catalysis.


Assuntos
Metais/química , Prebióticos , RNA/química , Ribose/química , Sais/química , Dióxido de Silício/química , Catálise
18.
Sci Rep ; 6: 30287, 2016 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-27456224

RESUMO

In the Avocado Sunblotch Viroid (ASBVd: 249-nt) from the Avsunviroidae family, a symmetric rolling-circle replication operates through an autocatalytic mechanism mediated by hammerhead ribozymes (HHR) embedded in both polarity strands. The concatenated multimeric ASBVd (+) and ASBVd (-) RNAs thus generated are processed by cleavage to unit-length where ASBVd (-) self-cleaves with more efficiency. Absolute scale small angle neutron scattering (SANS) revealed a temperature-dependent dimer association in both ASBVd (-) and its derived 79-nt HHR (-). A joint thermodynamic analysis of SANS and catalytic data indicates the rate-determining step corresponds to the dimer/monomer transition. 2D and 3D models of monomeric and dimeric HHR (-) suggest that the inter-molecular contacts stabilizing the dimer (between HI and HII domains) compete with the intra-molecular ones stabilizing the active conformation of the full-length HHR required for an efficient self-cleavage. Similar competing intra- and inter-molecular contacts are proposed in ASBVd (-) though with a remoter region from an extension of the HI domain.


Assuntos
RNA Viral/genética , Viroides/genética , Replicação Viral/genética , Conformação de Ácido Nucleico , Persea/virologia , RNA Viral/química , Termodinâmica , Viroides/química
19.
J Mol Evol ; 80(2): 86-97, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25487518

RESUMO

A fundamental problem in origins of life research is how the first polymers with the properties of nucleic acids were synthesized and incorporated into living systems on the prebiotic Earth. Here, we show that RNA-like polymers can be synthesized non-enzymatically from 5'-phosphate mononucleosides in salty environments. The polymers were identified and analyzed by gel electrophoresis, nanopore analysis, UV spectra, and action of RNases. The synthesis of phosphodiester bonds is driven by the chemical potential made available in the fluctuating hydrated and anhydrous conditions of hydrothermal fields associated with volcanic land masses.


Assuntos
Fontes Hidrotermais , Biogênese de Organelas , RNA/síntese química , Catálise , Cátions Monovalentes/química , Temperatura Alta , Nucleotídeos/química , Nucleotídeos/metabolismo , Polímeros/síntese química
20.
Carbohydr Res ; 402: 241-4, 2015 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-25498026

RESUMO

The existence of the ribose moiety in biomolecules poses two problems for prebiotic chemistry. First, the exclusive presence of the furanose isomer in RNA has to be accounted for since furanose is a minor form in solution and does not exist in crystals. Second, all D-ribose polymorphs are unstable in aqueous medium so that a stabilization mechanism has to be invoked. We observed that the adsorption on mineral surfaces as amorphous silica protects the sugar from degradation processes. Moreover, this silica surface, used as realistic chert model, is able to increase significantly the proportion of ribofuranose compared to ribopyranose forms. The interaction between surface and sugar was analyzed by 13C NMR. Our results show a very significant chemical and thermal stabilization of the adsorbed sugar by a silica surface and an almost twofold increase of ribofuranose compared to ribose in solution.


Assuntos
Ribose/química , Dióxido de Silício/química , Adsorção , Estabilidade de Medicamentos , Isomerismo , Propriedades de Superfície
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